Support \minuso (#2213)

* Support \minuso

* Update screenshots

* Add MathML version

* Add BIN spacing

* Update screenshots

* Add Unicode character

* Delete duplicate macro

Co-authored-by: Erik Demaine <edemaine@mit.edu>

src/macros.js

@@ -885,6 +885,14 @@ defineMacro("\u2984", "\\rBrace"); // blackboard bold }
 // TODO: Create variable sized versions of the last two items. I believe that
 // will require new font glyphs.
 
+// The stmaryrd function `\minuso` provides a "Plimsoll" symbol that
+// superimposes the characters \circ and \mathminus. Used in chemistry.
+defineMacro("\\minuso", "\\mathbin{\\html@mathml{" +
+    "{\\mathrlap{\\mathchoice{\\kern{0.145em}}{\\kern{0.145em}}" +
+    "{\\kern{0.1015em}}{\\kern{0.0725em}}\\circ}{-}}}" +
+    "{\\char`⦵}}");
+defineMacro("⦵", "\\minuso");
+
 //////////////////////////////////////////////////////////////////////
 // texvc.sty